Dozens of journalists staged a rare demonstration Tuesday morning in Myanmar's biggest city to protest a jail term given to a reporter who was working on a story about corruption.

Wearing black T-shirts with slogans saying, ''We don't want threat on Press Freedom,'' and carrying banners that read, ''Right to Information is life of democracy,'' nearly 60 reporters marched down a busy downtown Yangon street decrying the three-month prison sentence given to Ma Khine from the Daily Eleven newspaper.

She was convicted by a court in eastern Kayah state last month of trespassing, using abusive language and defamation.

Journalists have gained new freedoms under the reformist government of President Thein Sein, who since taking office in 2011 has abolished most censorship and allowed the publication of privately owned daily newspapers for the first time in almost five decades.

Whereas tighter controls have been imposed in China, prompting police to detain activists planning a protest in support of media freedom.

Previously in Myanmar, reporters worked under some of the tightest restrictions in the world, subject to routine state surveillance, phone taps and censorship for all publications.

Still, even under recent reforms, some publications have been sued for defamation, including by government agencies.

Ma Khine is the first journalist under Thein Sein's government to be given a prison sentence.

Ma Khine was sued by a lawyer after she visited her house for an interview for a story about corruption.

The lawyer was annoyed by her questioning and asked her to leave and later filed a lawsuit, according to Wai Phyo, chief editor of the Daily Eleven.

''The judge could have imposed a fine but deliberately gave the prison sentence not only to threaten the reporter but to threaten press freedom,'' he said.

Myint Kyaw, the general secretary of Myanmar Journalist Network, helped organise the protest march ''because we do not want the imprisonment of a journalist to become a precedent.''

Local and international media and watchdog organisations such as the World Association of Newspapers, Committee to Protect Journalists and Reporters Without Borders issued statements strongly condemning the prison sentence.

CHINESE ACTIVISTS DETAINED AHEAD OF PROTEST

Chinese authorities have detained some activists in the southern city of Guangzhou to try to derail a protest planned for Tuesday to commemorate a strike by reporters at an outspoken newspaper, several activists said.

The clampdown comes on the first anniversary of a rare newsroom strike at the Southern Weekly over censorship, which some experts say was the trigger for tighter controls on Chinese media in the past year under President Xi Jinping.

At least three activists contacted said they would not join the protest after being warned by police.

‘‘In recent days, those who were planning to mark the anniversary were either asked to meet (police), warned, put under house detention, forced to go on holiday ... or were detained,’’ said Wu Wei, also known by his pen-name Ye Du, the Guangzhou-based deputy head of the Independent Chinese Pen Center, which campaigns for freedom of expression in China.

Security was tight outside the gates of the Southern Media Group, which owns the Southern Weekly, with at least eight police vans and jeeps parked outside, and scores of uniformed and plainclothes police patrolling the area.

Police at the scene declined to comment.

Journalists at the weekly went on strike for several days last year after censors scrapped a New Year editorial calling for China to enshrine constitutional rights.

The strike ended after local propaganda officials promised to take a lighter hand with censorship. Prior to the run-in with the censors, the Southern Weekly had earned a reputation for pushing the boundaries in pursuing agenda-setting, hard-hitting news.

‘‘For the government, these kinds of commemorative events and street activities are not tolerated within their social stability framework,’’ said Wu.

‘‘They have ... pre-emptively clamped down on us.’’

On Saturday, police raided the home of activist Liang Songji, taking him into custody along with three others, according to two activists and online microblogging accounts. Sui Muqing, a rights lawyer, said police had forced their way into Liang’s home.

A rights lawyer in Guangzhou, Liu Shihui, was also detained and his whereabouts remained unknown, said Human Rights in China, an advocacy group.

Prior to Saturday’s detention, two other prominent rights activists in Guangzhou, Guo Feixiong and Liu Yuandong, were charged with assembling a crowd to ‘‘disrupt public order’’ during protests last year in support of the strike. The pair are expected to stand trial this month in Guangzhou.

In the protests last year outside the newspaper gates, some activists called for greater rights and democracy and lay wreaths of flowers in support of the journalists in a rare case of a politically charged street protest being tolerated by local authorities.

Since then, the government has tightened control over the media, punishing bloggers for spreading rumours on popular microblogging services, while media outlets nationwide have come under greater state scrutiny, according to many Chinese journalists.